26 April 2020

A study published in the Annals of Internal Medicine addresses the use of screening mammography in older women*. The goal of screening mammography (performed on a woman with no suspicious abnormality) is to reduce the likelihood of death from breast cancer. However, there are no randomized studies demonstrating this benefit in older women – they simply were not included in the early studies of screening mammography. Some national guidelines, including from the US Preventative Services Task Force, do not recommend screening mammography past age 75, noting that “the current evidence is insufficient to assess the balance of benefits and harms of screening mammography in women aged 75 years or older.” Some organizations, such as the American Society of Breast Surgeons and the American Cancer Society, recommend that screening mammograms continue as long as life expectancy is at least 10 years. In their Choosing Wisely statement, the American Geriatrics Society recommends that screening tests be considered in the context of life expectancy and take into account the risks of testing, overdiagnosis and overtreatment. 

This study used data from Medicare to compare death rates in women age 70 – 84 who underwent screening mammography versus those who stopped screening. Patients had no personal history of breast cancer and had a life expectancy of at least 10 years. 

There were slightly more breast cancers detected in the screening group, as expected: 5.5% in the women who underwent screening mammograms versus 3.9% in the women who did not. However, the researchers found that screening did not improve the likelihood of death from breast cancer. Among women age 70-74 there was 1 fewer breast cancer related death per 1000 women, over a period of 8 years, and this was not statistically significant. Among women age 75-84, there was no difference in breast cancer related deaths.

The authors concluded that screening mammography in older women does not significantly impact the likelihood of death from breast cancer. Limitations of this study include that it was an observational study, using information already in a database. The researchers could not adjust for certain factors including use of hormone replacement therapy, family history of breast cancer, and age at first pregnancy, which may impact breast cancer risk.  

A separate study* looked at the use of a decision aid in patients age 75 and older. The decision aid provided information about the risks and benefits of screening mammography. In this study of 546 patients, it was shown that receipt of the decision aid prior to an appointment with their physician resulted in women being more knowledgeable about screening mammography and having more discussions with their doctor about screening. In addition, 9% fewer women opted to undergo a screening mammogram. The authors concluded that the use of a decision aid may help reduce over screening in older women.

In the accompanying invited commentary, Drs. Elmore and Ngo-Metzger noted that in women age 74 with average health and life expectancy, screening mammograms prevent approximately 1 death per 1000 exams. However, 1000 women being screened can result in 79 – 96 of them experiencing a false positive (“false alarm”). They pointed out the challenges of screening mammography in older women in that the reduction in death from breast cancer can take many years, (during which the woman may die from other causes) but the potential harms are more immediate.

These two studies and the editorial raise important questions regarding the routine recommendation for screening mammography in older women. The decision whether or not to continue screening should be based on breast cancer risk as well as general health and risk of severe illness or death from other causes. When to stop screening mammography is a challenging, but important conversation to have with our older patients.

*If you are not able to access the full study and would like a copy, please email me: contact at drattai dot com

17 January 2016

In October 2015, the American Cancer Society (ACS) updated their screening mammography guidelines, raising a lot of questions and concerns as annual mammograms were no longer recommended for all women starting at age 40. The United States Preventative Services Task Force (USPSTF) released new guidelines on screening mammography last week. The new USPSTF guidelines recommend an individualized risk-based approach for women age 40-49, and mammographic screening every other year for women age 50-74. The task force acknowledged that screening mammography reduces the likelihood of dying from breast cancer, but noted that the benefit was the greatest for women age 60-69, and the benefit was small for women age 40-49. For younger women, they noted that screening mammography is associated with higher false positives (false alarms).

The conflicting guidelines published by the USPSTF, ACS, and other organizations have caused much confusion. Many women simply want to know what they should do. The reality is, screening mammography is a one size fits all tool, and as any woman knows, that doesn’t really work. The sensitivity (“effectiveness”) of mammograms will vary depending on a patient’s age, menstrual status, use of hormone therapy, body mass index, breast density, and other factors. It is unrealistic to expect that one test can account for all of those variables, as well as personal risk factors for breast cancer, and personal preferences regarding screening risks and benefits.

To state it very simply:

  • Mammograms may lead to improved survival from breast cancer by detecting some cancers early
  • Some breast cancers are so aggressive that early detection does not lead to improved survival
  • Mammograms are imperfect

It is important to note that the USPSTF and ACS recommendations apply to average risk women. Unfortunately, risk assessment is not routinely performed, and many factors associated with an increased risk, such as heavy alcohol intake and breast density, are not taken into account in the existing models. In an ideal world, we would swab a cheek, obtain some DNA, and then determine whether or not a woman is predisposed to develop breast cancer [I’m thinking beyond BRCA and other genetic testing here]. If we can determine that a 30 year old woman, even without a family of breast cancer, is predisposed to develop the disease, we can make educated screening recommendations (perhaps ultrasound and/or MRI, as mammograms are not very helpful in very young women).  If we can determine that a woman is highly likely to die of a heart attack by age 60, and has no cancer predisposition, she might make the decision to forego screening mammography. Unfortunately we’re not quite there yet, but there are genetic risk tests under development.

I recently spoke with a researcher specializing in cancer risk. We discussed that at the end of the day, multiple organizations will continue to look at the evidence and draw different conclusions, so in his opinion, it wasn’t realistic that we should expect consensus. Physicians, researchers, and organizations are currently spending a lot of time and effort arguing with each other about whether mammography should start at age 40, if mammograms should be performed every versus every other year, and when screening should stop. However, our time and efforts might be better spent by working together to address issues such as disparities in access to screening mammography and lack of access to quality mammography and breast care for many women.

Recognizing the variability of each woman and her breasts, acknowledging the uncertainties regarding the risks and benefits of screening, and focusing on a shared decision making approach might help reduce some of the confusion. In medicine, as in many areas in life, there is often more than one right answer. The same applies to screening mammography. Time to move beyond the one size fits all approach.

Additional Reading:
New York Times: Panel Reasserts Mammogram Advice
JAMA: A Public Health Framework for Screening Mammography: Evidence-Based vs Politically Mandated Care 
New York Times: Insurer Rewards Push Women Towards Mammograms
Forbes: A Turning Point in the Breast Cancer Screening Debate?
NPR Shots: Federal Panel Finalizes Mammogram Advice That Stirred Controversy
OncLive Final USPSTF Guidelines
Cornell Mammogram Decision Aid for Women age 40-49